1. Field of the Invention
The present invention relates to an image processing apparatus which enhances a luminance signal contained in an image so as to improve the resolution feeling (sharpness) of a captured image or the like.
2. Description of the Background Art
Image capture devices such as digital cameras and digital movie cameras generally perform contour enhancement processing to improve the resolution feeling of a captured image. In an image processing apparatus of a digital camera or the like, a Laplacian filter is applied to a luminance signal or the like to extract a contour component therefrom. The extracted contour component is added to the luminance signal, which is the original signal, so as to enhance the contour of the luminance signal.
A contour enhancement processing is performed using the contour component extracted from a luminance signal so as to improve the resolution feeling of an image having a large brightness difference easily and effectively. However, for example, when an image has a small brightness difference, or includes a black area on a red background (especially, including a boundary between deep red and black), it is difficult to extract the contour component, making it impossible to effectively improve the resolution feeling of the image.
In Japanese Patent Application Laid-open No. H8-275185, the contour component of a color signal is extracted, and the contour component of a luminance signal is reduced in size according to the size of the contour component of the color signal. More specifically, one control signal is generated based on the contour components of two color-difference signals, and then it is determined based on the generated control signal whether the contour component of the luminance signal is reduced to ¼.